Demonstration of a novel phase space painting method in a coupled lattice to mitigate space charge in high-intensity hadron beams

TL;DR

This paper introduces eigenpainting, a novel phase space painting method in coupled lattices, demonstrated at SNS to control beam distribution and mitigate space charge effects in high-intensity hadron accelerators.

Contribution

We demonstrate the first implementation of eigenpainting in a real accelerator, enabling full 4D phase space control and improved beam quality in high-intensity hadron beams.

Findings

Eigenpainting achieves a transverse emittance ratio of approximately 2.4.

The method produces a linear-force equilibrium distribution in the transverse plane.

Experimental results agree with particle-in-cell simulations, confirming effectiveness.

Abstract

Multi-turn charge-exchange injection is the primary method of creating high-intensity hadron beams in circular accelerators, and phase space painting during injection enables tailoring of the accumulated phase space distribution. A technique we call eigenpainting allows injection of particles into a single mode of a coupled ring, providing full four-dimensional control of the phase space distribution. Under ideal conditions, uniform eigenpainting generates a linear-force equilibrium distribution in the transverse plane, with zero volume in four-dimensional transverse phase space, even including space charge. We have implemented eigenpainting for the first time in the Spallation Neutron Source (SNS) Accumulator Ring. Injecting 8.8 $\mu$C of 800 MeV beam, we obtain a final ratio of intrinsic transverse emittances of $\approx$2.4. We analyze the effect of space charge on the final distribution through comparison of the reconstructed phase space to particle-in-cell simulations.